Relationship of Weight Outcomes and Severity of Autism Spectrum Disorder (ASD) in the Study to Explore Early Development (SEED)

Background: Being overweight (OW) or obese (OB) is common in the general population, with almost 1/3 of children affected.  Existing literature indicates that school-age children with autism spectrum disorder (ASD) or developmental disorders (DD) are at greater risk for OW or OB. These findings and corresponding risk factors have not yet been addressed in large populations of preschool children (< 6 years old). 

Objectives: We examined child weight outcomes in preschool children, across ASD, DD, and population control (POP) groups and the association between severity of ASD symptoms and OW or OB.

Methods: The Study to Explore Early Development (SEED) is a multi-site case-control study of children (3-5 years), comparing 3 groups: ASD (n=668), DD (n=914), and POP (n=884).  Children in the DD and POP groups did not have a diagnosis of ASD.  All children had parent interviews (medical and treatment history), cognitive assessment, behavioral screening questionnaires and child anthropometric measurements (during dysmorphology exam).  Children in the ASD group had comprehensive ASD diagnostic evaluations (ADOS and ADI-R) and clinician-completed DSM-5 checklists with severity of symptoms noted, ranging mild to severe. Child age- and sex-specific BMI percentiles and z-scores were calculated using CDC Growth Charts 2000, and classified with BMI-for-age: underweight (UW) <5^th percentile; normal-weight 5^th to <85^th percentile; OW and OB > 85^th percentile. Associations between group membership and demographics were determined using chi-square tests.  The association between obesity and group membership and severity of ASD symptoms was measured using a logistic regression model, with a p-value of <0.05 as significant.  All analyses were conducted in SAS version 9.3 (SAS Institute, Cary, NC).

Results:  Children in the ASD group had the highest percentage of males (81.7%) compared to DD (65.1%) and POP (53.1%) and were less likely to be white (57.5%), compared to DD (65.1%) and POP (69.9%). A chi-square test found a significant association between group membership and child weight status (p<0.0005).  Children with ASD and DD had the highest frequency of OW or OB (ASD 27.5%, DD 25.0%) compared to POP children (19.5 %).  Compared to POP children, children with ASD had 1.57 (CI: 1.24, 2.00) times the odds of being OW or OB (p= 0.002), and children with DD had 1.38 (CI: 1.10, 1.72) times the odds of being OW or OB (p = 0.001).  There was a significant positive association between severity of ASD symptoms and weight status based on the Mantel-Haenszel chi-square test (p = 0.026).

Conclusions: Our findings suggest that children aged 3-5 years with ASD or DD have higher odds of being OW or OB than children in the POP group.  Children in the ASD group with more severe symptoms of ASD were more likely to be OW or OB.  Further analyses will be completed to parse out the contribution of other demographic, medical, developmental, behavioral, and treatment factors to the increased risk of OW or OB. Understanding factors associated with or contributing to excess weight gain will provide important information for clinicians and families caring for children with ASD and DD.